1. Field of the Invention
This invention relates to a top-shooter thermal inkjet recording head from which an ink drop is expelled toward a recording medium by means of thermal energy, and a recording apparatus using the inkjet recording head.
2. Description of the Prior Art
Some known method for manufacturing a top-shooter thermal inkjet recording head are described as follows:
Hewllett Packard Journal 36, 5 (1985) discloses using a photoresist to form an ink passage on a substrate having a heater for expelling an ink drop, and aligning and attaching an orifice plate having an ink nozzle to the substrate.
Japanese patent application publication 61-154947 discloses a dissolvable Ni or resin film to pattern an ink passage in a substrate having a heater for expelling an ink drop, cover and cure the patterned resin with an epoxide resin film. Then, the patterned resin is dry-etched to form an ink nozzle. The dissolvable Ni or resin film id dissolved to form the ink passage.
Japanese patent application publication 8-207291 discloses using a resin to form an ink passage on a substrate having a heater for expelling an ink drop. A resin film is attached on the substrate, and photo-etched to form an ink nozzle.
Especially, the method that uses only photo-etching processes enables forming ink nozzles at a high density and on a large scale.
In a conventional inkjet recording head, a resin thin film is used as the orifice plate. However, it is difficult to form the orifice plate having a thickness less than 10 xcexcm from a manufacturing point of view. For example, the method disclosed in Japanese patent application publication 61-154947 forms the orifice plate by spin-coating a liquid resin on the ink passage pattern, because the passage pattern has many pits and projections. Thus, it is difficult to make the resin film around the ink nozzle thin and uniform over the substrate. The method disclosed in Japanese patent application publication 8-207291 attaches a resin film over ink passage on the substrate. However, it is difficult to attach a thin film having a thickness less than 10 xcexcm from a manufacturing point of view.
Here, the relationship between the size of ejected ink drops and the thickness of the orifice plate will be explained. FIG. 1 is a vertical cross section of a conventional top-shooter inkjet recording head having an ink feed channel. FIG. 2 is a cross section taken along line IIxe2x80x94II of FIG. 1. Ink is fed from a back surface of the substrate 1 to an ink nozzle 10 through an ink feed inlet 6, an ink feed channel 7, a common ink passage 8, and an separate ink passage 9. Electric power is fed to a heater 2 to generate nucleate boiling in the ink for expelling an ink drop. The expanding force of the resultant bubble ejects the ink drop from the ink nozzle 10.
This type of inkjet head has the ink nozzle 10 extending vertically through the orifice plate. If the sum of the thickness of a barrier layer 3 and the orifice plate 16 is smaller than about 30 xcexcm, the amount of expelled ink is constant, and no cavitation occurs to the heater. Japanese patent application publications 7-227967 and 8-20110 describe that the amount of expelled ink is proportional to the ink volume located over the heater 2. According to these patent publications, a proportional constant is about 0.5 to 0.7, depending on the head structure. Therefore, in order to form an ink drop having a volume of about 1 pico-liter (pl) (15xc3x9715xc3x975 xcexcm3), the sum of the thickness of the barrier layer 3 and the orifice plate 16 must be less than at least 10 xcexcm. However, it is difficult to form an orifice plate having a thickness of less than 10 xcexcm using conventional methods. As a result, it is difficult to make an ink drop having a volume less than or equal to 3 pl.
An object of the present invention is to provide an inkjet recording head which can expel an ink drop having a volume less than or equal to 3 pl.
Another object of the present invention is to provide a method for manufacturing an inkjet recording head which can expel an ink drop having a volume less than or equal to 3 pl.
The above disadvantages associated with the prior art are overcome by the present invention of an inkjet recording head, having: a substrate having a heater for ejecting an ink drop, and being formed with an ink feed inlet; an orifice plate having an ink nozzle formed facing the heater, and a barrier layer provided between the substrate and the orifice plate, the barrier layer having an ink passage that brings the ink feed inlet and the ink nozzle into fluid communication with each other; the barrier layer being formed from a negative photosensitive resin, and the orifice plate including a metallic thin film having a thickness in a range of about 0.1 to 2.0 xcexcm.
According to the present invention, the inkjet recording head can expel an ink drop having a volume less than or equal to 1 pl. Additionally, it is easy to manufacture the inkjet recording head having a water-repellent film on a surface of the head by simple processes. Throughput of manufacturing can be improved. A fine color image can be printed at a high speed and at a lower cost.
The present invention further features an ink cassette, having an inkjet recording head including: a substrate having a heater for ejecting an ink drop, and being formed with an ink feed inlet; an orifice plate having an ink nozzle formed facing the heater; and a barrier layer provided between the substrate and the orifice plate, the barrier layer having an ink passage that brings the ink feed inlet and the ink nozzle into fluid communication with each other; the barrier layer being formed from a negative photosensitive resin, and the orifice plate including a metallic thin film having a thickness in a range of about 0.1 to 2.0 xcexcm.
According to the present invention, an ink tank of the ink cartridge can be maintained at a normal pressure. And, a volume of the ink tank can be increased.
The present invention features a recording apparatus, having an inkjet recording head including: a substrate having a heater for ejecting an ink drop, and being formed with an ink feed inlet; an orifice plate having an ink nozzle formed facing the heater; and a barrier layer provided between the substrate and the orifice plate, the barrier layer having an ink passage that brings the ink feed inlet and the ink nozzle into fluid communication with each other; the barrier layer being formed from a negative photosensitive resin, and the orifice plate including a metallic thin film having a thickness in a range of about 0.1 to 2.0 xcexcm.
According to the present invention, the number of times the inkjet recording needs to be cleaned can be reduced.
The present invention features a method for manufacturing an inkjet recording head, having the steps of: providing a substrate having a heater for ejecting an ink drop, and being formed with an ink feed inlet; providing an orifice plate having an ink nozzle formed facing the heater; and providing a barrier layer provided between the substrate and the orifice plate. The barrier, layer has an ink passage that brings the ink feed inlet and the ink nozzle into fluid communication with each other. The barrier layer is formed from a negative photosensitive resin. And the orifice plate includes a metallic thin film having a thickness in a range of about 0.1 to 2.0 xcexcm.
According to the present invention, a high level of throughput of manufacturing an inkjet recording head is obtained.